1. Field of the Invention
The present invention relates to an improved apparatus for the conveying and exchanging of a pouring tube for a vessel for pouring molten metal from the bottom, in which a movable sealing plate and/or a replacement pouring tube attached to a movable plate is/are placed side by side by a common transverse edge next to a movable plate carrying a pouring tube to be replaced, or against a sealing plate to be moved away from the pouring gate, said movable replacement plate and said plate which is to be replaced being mounted to slide on guides which are suitable to transmit an upward pressure and to guide the displacement by transferring the plates and the pouring tubes parallel to each other under the action of a pneumatic jack in a direction perpendicular to the axis of the pouring gate, from a loading position to a working position in the axis of the pouring gate of the vessel, and from the working position to a clearing position, so as to permit the exchanging of the tube without raising the vessel.
It is mainly used in iron smelting in plants for continuous casting in order to place interchangeable pouring tubes in position, in alignment with the axis of the pouring gate of a metallurgical vessel, below said vessel.
The pouring tubes, which are intended to guide the molten metal into a mould or ingot mould hole, are heavily stressed wearing parts. This is the case to the point where their service life restricts the pouring time.
2. Description of the Prior Art
From EP-A-0192019, (U.S. Pat. No. 4,669,528) an apparatus for the conveying and exchanging of a pouring tube is known, having a detachably fitted plate for an iron-smelting or metallurgical vessel which can be sealed at the bottom by means of a stopper rod or by a sliding gate.
The conveying and exchanging apparatus comprises a movable refractory plate which can slide, under the action of a jack, along an upper reference plate, from a loading position into a working position or a sealing position, in alignment with the axis of the pouring gate.
The guide rails push the movable plate, in tight contact, against the upper reference plate under the effect of an upward pressure transmitted by a first extremity of levers on which helical springs act downwards on an opposite extremity, which springs are supported on the frame of the conveying and exchanging apparatus.
The guide rails are parallel to one another and are arranged at a slight inclination at an angle of 5.degree. to 10.degree. relative to the plane of reference. An apparatus of this kind readily permits the replacement of a pouring tube having a movable refractory detachable plate without raising the header.
A double-action pneumatic jack ensures the linear displacement of the movable plate bearing the pouring tube. The replacement tube is conveyed, by pivoting about a substantially horizontal axis, to the mould or the ingot mould hole, so as to permit exchanging the pouring tube without having to raise the header.
In said known apparatus, the movable plate which is intended to slide along a rectilinear path along the upper reference plate forms, relative to said upper reference plate, an inclined surface, the pitch of which is determined by the slope of the path of the guide rails.
The pitch of the guide rails relative to the reference plane of the upper plate makes it possible to obtain a gradual securing of the movable plate attached to the pouring tube when the latter is brought into alignment with the pouring opening, but it has the disadvantage that the joint between the two plates in the vicinity of the pouring gate opening is not tight. In fact, the parallelism between the bottom plate and the movable plate bearing the pouring tube is not perfect at the time of the engagement of the movable plate in the sealing zone surrounding the pouring gate opening. Liquid metal can penetrate between the upper reference plate and the movable plate. When hardening, the metal which has penetrated forms a crust which changes the evenness of the contact surfaces and gives rise to the danger of jamming of the movable plate and to be a cause for the non-sealing of a contact zone of the two plates in the immediate vicinity of the pouring opening.